Bones of the Ear - Anatomy Pictures and Information Home > Skeletal System > Bones of the Head and Neck > Bones of the Ear Bones of the Ear The bones of the ear, also known as the auditory ossicles, are the three smallest bones in the human body. These bones play an important role in the sense of hearing by transmitting sounds to the inner ear. Anatomy The three auditory ossicles – the malleus, incus, and stapes – are tiny bones found in the middle ear. Each bone is named in Latin for its shape: Malleus means hammer or mallet Incus means anvil Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Full Bones of the Ear Description [Continued from above] . . . The hammer-like malleus is the most lateral of the ossicles and has a large, rounded head on its superior end, which tapers to a narrow neck and handle on its inferior end.

It is connected to the tympanic membrane, or eardrum, at the handle and forms a synovial joint with the incus at the head. The anvil-like incus is the middle ossicle that forms synovial joints with the malleus on its lateral side and the stapes on its medial side. The incus is widest where it meets the malleus and tapers to a thinner projection known as the lenticular process where it meets the stapes. The stirrup-shaped stapes is the smallest ossicle with a hollow space in the middle. The stapes begins with a tiny cylindrical head where it meets the incus before splitting into two parallel columns of bone known as the anterior and posterior crus. These columns end suddenly at the flat, oblong base that rests within the oval window and conducts sounds into the inner ear. Physiology The main function of the auditory ossicles is the conduction of sounds to the inner ear where they transduced into nerve signals and sent onward to the brain. Sound waves entering the ear pass through the auditory canal of the outer ear and trigger vibrations in the tympanic membrane. These vibrations are conducted into the malleus, which is connected to the tympanic membrane through its handle region.

The malleus conducts its vibrations into the incus through its synovial joint and the incus likewise conducts vibrations into the stapes. Finally, the vibrations of the stapes push its base back and forth through the oval window to form new waves in the endolymph of the inner ear. The secondary function of the auditory ossicles is the attenuation of sound waves to control the volume of sounds reaching the inner ear. A pair of skeletal muscles, the tensor tympani and stapedius, contract to reduce the vibration of the malleus and stapes in response to loud sounds. Sound attenuation is very important in daily life by limiting the sounds produced during chewing and the sound of one’s own voice while talking. Prepared by Tim Taylor, Anatomy and Physiology Instructor X. The Organs of the Senses and the Common Integument. 1d. 3. The Auditory Ossicles. Gray, Henry. 1918. Anatomy of the Human Body. 2 The head (capitulum mallei) is the large upper extremity of the bone; it is oval in shape, and articulates posteriorly with the incus, being free in the rest of its extent.

The facet for articulation with the incus is constricted near the middle, and consists of an upper larger and lower smaller part, which form nearly a right angle with each other. Opposite the constriction the lower margin of the facet projects in the form of a process, the cog-tooth or spur of the malleus. FIG. 916 Left malleus. A. From behind. B. From within. ( See enlarged image ) The neck (collum mallei) is the narrow contracted part just beneath the head; below it, is a a prominence, to which the various processes are attached. 4 The manubrium mallei (handle) is connected by its lateral margin with the tympanic membrane. It is directed downward, medialward, and backward; it decreases in size toward its free end, which is curved slightly forward, and flattened transversely. On its medial side, near its upper end, is a slight projection, into which the tendon of the Tensor tympani is inserted.

5 The anterior process (processus anterior [Folii]; processus gracilis) is a delicate spicule, which springs from the eminence below the neck and is directed forward to the petrotympanic fissure, to which it is connected by ligamentous fibers. In the fetus this is the longest process of the malleus, and is in direct continuity with the cartilage of Meckel. 6 The lateral process (processus lateralis; processus brevis) is a slight conical projection, which springs from the root of the manubrium; it is directed laterally, and is attached to the upper part of the tympanic membrane and, by means of the anterior and posterior malleolar folds, to the extremities of the notch of Rivinus. 7 The Incus (Fig. 917) has received its name from its supposed resemblance to an anvil, but it is more like a premolar tooth, with two roots, which differ in length, and are widely separated from each other. It consists of a body and two crura.

15 The two crura (crus anterius and crus posterius) diverge from the neck and are connected at their ends by a flattened oval plate, the base (basis stapedis), which forms the foot-plate of the stirrup and is fixed to the margin of the fenestra vestibuli by a ring of ligamentous fibers. Of the two crura the anterior is shorter and less curved than the posterior. FIG. 917 Left incus. A. From within. B. From the front. ( See enlarged image ) FIG. 918 A. Left stapes. B. Base of stapes, medial surface. ( See enlarged image ) Articulations of the Auditory Ossicles (articulationes ossiculorum auditus).The incudomalleolar joint is a saddle-shaped diarthrosis; it is surrounded by an articular capsule, and the joint cavity is incompletely divided into two by a wedge-shaped articular disk or meniscus.

The incudostapedial joint is an enarthrosis, surrounded by an articular capsule; some observers have described an articular disk or meniscus in this joint; others regard the joint as a syndesmosis. 17 Ligaments of the Ossicles (ligamenta ossiculorum auditus).The ossicles are connected with the walls of the tympanic cavity by ligaments: three for the malleus, and one each for the incus and stapes. 18 The anterior ligament of the malleus (lig. mallei anterius) is attached by one end to the neck of the malleus, just above the anterior process, and by the other to the anterior wall of the tympanic cavity, close to the petrotympanic fissure, some of its fibers being prolonged through the fissure to reach the spina angularis of the sphenoid. 25 The Tensor tympani, the larger, is contained in the bony canal above the osseous portion of the auditory tube, from which it is separated by the septum canalis musculotubarii.

It arises from the cartilaginous portion of the auditory tube and the adjoining part of the great wing of the sphenoid, as well as from the osseous canal in which it is contained. Passing backward through the canal, it ends in a slender tendon which enters the tympanic cavity, makes a sharp bend around the extremity of the septum, and is inserted into the manubrium of the malleus, near its root. It is supplied by a branch of the mandibular nerve through the otic ganglion. FIG. 919 Chain of ossicles and their ligaments, seen from the front in a vertical, transverse section of the tympanum. (Testut.) ( See enlarged image ) The Stapedius arises from the wall of a conical cavity, hollowed out of the interior of the pyramidal eminence; its tendon emerges from the orifice at the apex of the eminence, and, passing forward, is inserted into the posterior surface of the neck of the stapes. It is supplied by a branch of the facial nerve. 27 Actions.The Tensor tympani draws the tympanic membrane medialward, and thus increases its tension.

The Stapedius pulls the head of the stapes backward and thus causes the base of the bone to rotate on a vertical axis drawn through its own center; the back part of the base is pressed inward toward the vestibule, while the forepart is withdrawn from it. By the action of the muscle the tension of the fluid within the internal ear is probably increased. 28 The Mucous Membrane of the Tympanic Cavity is continuous with that of the pharynx, through the auditory tube. It invests the auditory ossicles, and the muscles and nerves contained in the tympanic cavity; forms the medial layer of the tympanic membrane, and the lateral layer of the secondary tympanic membrane, and is reflected into the tympanic antrum and mastoid cells, which it lines throughout. It forms several vascular folds, which extend from the walls of the tympanic cavity of the ossicles; of these, one descends from the roof of the cavity to the head of the malleus and upper margin of the body of the incus, a second invests the Stapedius muscle: other folds invest the chorda tympani nerve and the Tensor tympani muscle.

These folds separate off pouch-like cavities, and give the interior of the tympanum a somewhat honey-combed appearance. One of these pouches, the pouch of Prussak, is well-marked and lies between the neck of the malleus and the membrana flaccida. Two other recesses may be mentioned: they are formed by the mucous membrane which envelops the chorda tympani nerve and are situated, one in front of, and the other behind the manubrium of the malleus; they are named the anterior and posterior recesses of Troltsch. In the tympanic cavity this membrane is pale, thin, slightly vascular, and covered for the most part with columnar ciliated epithelium, but over the pyramidal eminence, ossicles, and tympanic membrane it possesses a flattened non-ciliated epithelium. In the tympanic antrum and mastoid cells its epithelium is also non-ciliated.

In the osseous portion of the auditory tube the membrane is thin; but in the cartilaginous portion it is very thick, highly vascular, and provided with numerous mucous glands; the epithelium which lines the tube is columnar and ciliated. 29 Vessels and Nerves.The arteries are six in number. Two of them are larger than the others, viz., the tympanic branch of the internal maxillary, which supplies the tympanic membrane; and the stylomastoid branch of the posterior auricular, which supplies the back part of the tympanic cavity and mastoid cells. The smaller arteries arethe petrosal branch of the middle meningeal, which enters through the hiatus of the facial canal; a branch from the ascending pharyngeal, and another from the artery of the pterygoid canal, which accompany the auditory tube; and the tympanic branch from the internal carotid, given off in the carotid canal and perforating the thin anterior wall of the tympanic cavity. The veins terminate in the pterygoid plexus and the superior petrosal sinus.

The nerves constitute the tympanic plexus, which ramifies upon the surface of the promontory. The plexus is formed by (1) the tympanic branch of the glossopharyngeal; (2) the caroticotympanic nerves; (3) the smaller superficial petrosal nerve; and (4) a branch which joins the greater superficial petrosal. 30 The tympanic branch of the glossopharyngeal (Jacobsons nerve) enters the tympanic cavity by an aperture in its floor close to the labyrinthic wall, and divides into branches which ramify on the promontory and enter into the formation of the tympanic plexus. The superior and inferior caroticotympanic nerves from the carotid plexus of the sympathetic pass through the wall of the carotid canal, and join the branches of the tympanic branch of the glossopharyngeal. The branch to the greater superficial petrosal passes through an opening on the labyrinthic wall, in front of the fenestra vestibuli.

The smaller superficial petrosal nerve, from the otic ganglion, passes backward through a foramen in the middle fossa of the base of the skull (sometimes through the foramen ovale), and enters the anterior surface of the petrous part of the temporal bone through a small aperture, situated lateral to the hiatus of the facial canal; it courses downward through the bone, past the genicular ganglion of the facial nerve, receiving a connecting filament from it, and enters the tympanic cavity, where it communicates with the tympanic branch of the glossopharyngeal, and assists in forming the tympanic plexus. 31 The branches of distribution of the tympanic plexus are supplied to the mucous membrane of the tympanic cavity; a branch passes to the fenestra vestibuli, another to the fenestra cochleæ, and a third to the auditory tube. The smaller superficial petrosal may be looked upon as the continuation of the tympanic branch of the glossopharyngeal through the plexus to the otic ganglion.

Ossicle - definition of ossicle by The Free Dictionary Ossicle - definition of ossicle by The Free Dictionary Related to ossicle: middle ear ossicles os·si·cle A small bone, especially one of the three bones of the middle ear. [Latin ossiculum, diminutive of os, bone; see ost- in the Appendix of Indo-European roots.] os·sic′u·lar (ŏ-sĭk′yə-lər), os·sic′u·late (-lĭt) adj. ossicle (Anatomy) a small bone, esp one of those in the middle ear [C16: from Latin ossiculum, from os bone] ossicular adj os•sic•u•lar (ɒˈsɪk yə lər) adj. os·si·cle (ŏs′ĭ-kəl) A small bone, especially one of the three located in the middle ear (the incus, malleus, and stapes) that transmit sound vibrations from the eardrum to the inner ear.

ThesaurusAntonymsRelated WordsSynonymsLegend: bonelet , ossiculum bone , os - rigid connective tissue that makes up the skeleton of vertebrates auditory ossicle - ossicles of the middle ear that transmit acoustic vibrations from the eardrum to the inner ear middle ear , tympanic cavity , tympanum - the main cavity of the ear; between the eardrum and the inner ear Translations ossicle n (of the ear) huesecillo (del oído) Want to thank TFD for its existence? Tell a friend about us , add a link to this page, or visit the webmaster's page for free fun content . Link to this page: radial References in periodicals archive ? Our task is to show that ossicle morphology and sculpture may provide a novel tool for taxonomic studies. A new deepwater species of the genus Apogonichthyoides (Apogonidae) from the Timor Sea, north-western Australia A large plaque very rarely causes a partial ossicle fixation, but no available studies have proved any hearing loss related to the myringosclerotic plaques in and of themselves.

Subcutaneous peroneus longus tendon rupture associated with os peroneum Fracture In the Fabrica Vesalius had dismissed such speculation in a splendidly sarcastic disquisition on the occult belief in the luz or Albadaran, a bone the size of a chickpea, supposedly impervious to decay, from which the entire person of the deceased would be reconstituted at the day of judgment: playfully identifying it with "the inner ossicle of the right big toe," and observing that it "can in fact be broken and burnt just like other bones," Vesalius consigned the subject of the soul to the province of theologians, insisting that the metaphysics of immortality were no concern of the anatomical scientist. Fitness farm fun!

Body Parts Spelling Bee Words Beginner (6 and under) hip head eye temple face cheek jaw scalp arm leg limb breast vein kidney ureter cord pons dura tube nail Junior (7 and 8) skin skeleton orbit pinna socket globe nasal space ear canal brain stem spinal cord vertebra tonsil spleen root lymph vocal cord nervous system frontal lobe cornea anvil Advanced (9 and 10) cranium hard palate soft palate suture lymph node dendrite hormone sclera stirrup olfactory vomer uvula epiglottis cricoid pharnyx pectoral intercostal acetabulum vena cava subclavian Super (11 and 12) ganglion bronchiole cementum malleolus zygomatic lacrimal ossicle ethmoid epigastric sacroiliac inguinal mesentery trigeminal ischium lymphocyte corpus callosum photoreceptor pterygoid maxillary sinus foramen magnum Be witty in the city!

Enlow's integrative approach to human skeletal development and morphology, and is based on extensive studies that date from 1955 to 1990 from human, monkey, cat, rabbit and rat craniofacial and postcranial specimens that represent various projects ranging from the ontogeny of auditory ossicle histology to the cleft palate. The Auditory Ossicles - Human Anatomy FIG. 918 A. Left stapes. B. Base of stapes, medial surface. Articulations of the Auditory Ossicles (articulationes ossiculorum auditus).The incudomalleolar joint is a saddle-shaped diarthrosis; it is surrounded by an articular capsule, and the joint cavity is incompletely divided into two by a wedge-shaped articular disk or meniscus. The incudostapedial joint is an enarthrosis, surrounded by an articular capsule; some observers have described an articular disk or meniscus in this joint; others regard the joint as a syndesmosis.

Ligaments of the Ossicles (ligamenta ossiculorum auditus).The ossicles are connected with the walls of the tympanic cavity by ligaments: three for the malleus, and one each for the incus and stapes. The anterior ligament of the malleus (lig. mallei anterius) is attached by one end to the neck of the malleus, just above the anterior process, and by the other to the anterior wall of the tympanic cavity, close to the petrotympanic fissure, some of its fibers being prolonged through the fissure to reach the spina angularis of the sphenoid. The superior ligament of the malleus (lig. mallei superius) is a delicate, round bundle which descends from the roof of the epitympanic recess to the head of the malleus. The lateral ligament of the malleus (lig. mallei laterale; external ligament of the malleus) is a triangular band passing from the posterior part of the notch of Rivinus to the head of the malleus.

Helmholtz described the anterior ligament and the posterior part of the lateral ligament as forming together the axis ligament around which the malleus rotates. The posterior ligament of the incus (lig. incudis posterius) is a short, thick band connecting the end of the short crus of the incus to the fossa incudis. A superior ligament of the incus (lig. incudis superius) has been described, but it is little more than a fold of mucous membrane. The vestibular surface and the circumference of the base of the stapes are covered with hyaline cartilage; that encircling the base is attached to the margin of the fenestra vestibuli by a fibrous ring, the annular ligament of the base of the stapes (lig. annulare baseos stapedis). The Muscles of the Tympanic Cavity (musculi ossiculorum auditus) are the Tensor tympani and Stapedius.

The Tensor tympani, the larger, is contained in the bony canal above the osseous portion of the auditory tube, from which it is separated by the septum canalis musculotubarii. It arises from the cartilaginous portion of the auditory tube and the adjoining part of the great wing of the sphenoid, as well as from the osseous canal in which it is contained. Passing backward through the canal, it ends in a slender tendon which enters the tympanic cavity, makes a sharp bend around the extremity of the septum, and is inserted into the manubrium of the malleus, near its root. It is supplied by a branch of the mandibular nerve through the otic ganglion. FIG. 919 Chain of ossicles and their ligaments, seen from the front in a vertical, transverse section of the tympanum.

(Testut.) The Stapedius arises from the wall of a conical cavity, hollowed out of the interior of the pyramidal eminence; its tendon emerges from the orifice at the apex of the eminence, and, passing forward, is inserted into the posterior surface of the neck of the stapes. It is supplied by a branch of the facial nerve. Actions.The Tensor tympani draws the tympanic membrane medialward, and thus increases its tension. The Stapedius pulls the head of the stapes backward and thus causes the base of the bone to rotate on a vertical axis drawn through its own center; the back part of the base is pressed inward toward the vestibule, while the forepart is withdrawn from it. By the action of the muscle the tension of the fluid within the internal ear is probably increased. The Mucous Membrane of the Tympanic Cavity is continuous with that of the pharynx, through the auditory tube.

It invests the auditory ossicles, and the muscles and nerves contained in the tympanic cavity; forms the medial layer of the tympanic membrane, and the lateral layer of the secondary tympanic membrane, and is reflected into the tympanic antrum and mastoid cells, which it lines throughout. It forms several vascular folds, which extend from the walls of the tympanic cavity of the ossicles; of these, one descends from the roof of the cavity to the head of the malleus and upper margin of the body of the incus, a second invests the Stapedius muscle: other folds invest the chorda tympani nerve and the Tensor tympani muscle. These folds separate off pouch-like cavities, and give the interior of the tympanum a somewhat honey-combed appearance. One of these pouches, the pouch of Prussak, is well-marked and lies between the neck of the malleus and the membrana flaccida.

Two other recesses may be mentioned: they are formed by the mucous membrane which envelops the chorda tympani nerve and are situated, one in front of, and the other behind the manubrium of the malleus; they are named the anterior and posterior recesses of Troltsch. In the tympanic cavity this membrane is pale, thin, slightly vascular, and covered for the most part with columnar ciliated epithelium, but over the pyramidal eminence, ossicles, and tympanic membrane it possesses a flattened non-ciliated epithelium. In the tympanic antrum and mastoid cells its epithelium is also non-ciliated. In the osseous portion of the auditory tube the membrane is thin; but in the cartilaginous portion it is very thick, highly vascular, and provided with numerous mucous glands; the epithelium which lines the tube is columnar and ciliated. Vessels and Nerves.The arteries are six in number.

Two of them are larger than the others, viz., the tympanic branch of the internal maxillary, which supplies the tympanic membrane; and the stylomastoid branch of the posterior auricular, which supplies the back part of the tympanic cavity and mastoid cells. The smaller arteries arethe petrosal branch of the middle meningeal, which enters through the hiatus of the facial canal; a branch from the ascending pharyngeal, and another from the artery of the pterygoid canal, which accompany the auditory tube; and the tympanic branch from the internal carotid, given off in the carotid canal and perforating the thin anterior wall of the tympanic cavity. The veins terminate in the pterygoid plexus and the superior petrosal sinus. The nerves constitute the tympanic plexus, which ramifies upon the surface of the promontory. The plexus is formed by (1) the tympanic branch of the glossopharyngeal; (2) the caroticotympanic nerves; (3) the smaller superficial petrosal nerve; and (4) a branch which joins the greater superficial petrosal.

The tympanic branch of the glossopharyngeal (Jacobsons nerve) enters the tympanic cavity by an aperture in its floor close to the labyrinthic wall, and divides into branches which ramify on the promontory and enter into the formation of the tympanic plexus. The superior and inferior caroticotympanic nerves from the carotid plexus of the sympathetic pass through the wall of the carotid canal, and join the branches of the tympanic branch of the glossopharyngeal. The branch to the greater superficial petrosal passes through an opening on the labyrinthic wall, in front of the fenestra vestibuli.

The smaller superficial petrosal nerve, from the otic ganglion, passes backward through a foramen in the middle fossa of the base of the skull (sometimes through the foramen ovale), and enters the anterior surface of the petrous part of the temporal bone through a small aperture, situated lateral to the hiatus of the facial canal; it courses downward through the bone, past the genicular ganglion of the facial nerve, receiving a connecting filament from it, and enters the tympanic cavity, where it communicates with the tympanic branch of the glossopharyngeal, and assists in forming the tympanic plexus. The branches of distribution of the tympanic plexus are supplied to the mucous membrane of the tympanic cavity; a branch passes to the fenestra vestibuli, another to the fenestra cochleæ, and a third to the auditory tube. The smaller superficial petrosal may be looked upon as the continuation of the tympanic branch of the glossopharyngeal through the plexus to the otic ganglion. In addition to the tympanic plexus there are the nerves supplying the muscles.

The Tensor tympani is supplied by a branch from the mandibular through the otic ganglion, and the Stapedius by a branch from the facial. The chorda tympani nerve crosses the tympanic cavity. It is given off from the sensory part of the facial, about 6 mm. before the nerve emerges from the stylomastoid foramen. It runs from below upward and forward in a canal, and enters the tympanic cavity through the iter chordæ posterius, and becomes invested with mucous membrane. It traverses the tympanic cavity, crossing medial to the tympanic membrane and over the upper part of the manubrium of the malleus to the carotid wall, where it emerges through the iter chordæ anterius (canal of Huguier). ear bone | anatomy | Britannica.com Ear bone Alternative Titles: auditory ossicle, ossicula auditus, ossicular chain Related Topics mammal Ear bone, also called Auditory Ossicle, any of the three tiny bones in the middle ear of all mammals. These are the malleus , or hammer , the incus , or anvil , and the stapes , or stirrup .

Together they form a short chain that crosses the middle ear and transmits vibrations caused by sound waves from the eardrum membrane to the liquid of the inner ear . The malleus resembles a club more than a hammer, whereas the incus looks like a premolar tooth with an extensive root system. The stapes does closely resemble a stirrup. The top or head of the malleus and the body of the incus are held together by a tightly fitting joint and are seated in the attic, or upper portion, of the eardrum cavity. The handle of the malleus adheres to the upper half of the drum membrane. Three small ligaments hold the head of the malleus, and a fourth attaches a projection (called the short process) from the incus to a slight depression in the back wall of the cavity. The long process of the incus is bent near the lower end and carries a small knoblike bone that is jointed loosely to the head of the stapes—the third and smallest of the ossicles. The stapes lies in a horizontal position at right angles with the long process of the incus.

There are two openings in the wall of the bony labyrinth and the stapes footplate fits perfectly in one of these openings—an oval-shaped window, where it is held in place by yet another ligament called the annular ligament. There are two tiny muscles in the middle ear, which serve to alter the tension on the ear bones and thus the intensity (degree of loudness) of sounds. One, the tensor tympani , is attached to the handle of the malleus (itself attached to the eardrum membrane) and by its contraction tends to draw the malleus inward, thus increasing drum membrane tension. The second, called stapedius , tends to pull the footplate of the stapes out of the oval window. This is accomplished by tipping the stirrup, or stapes, backward. Learn More in these related articles: Chapter 28 On the Ossicles Which Resemble a Sesame Seed Book One -- The things that sustain and support the entire body, and what braces and attaches them all.

[the bones and the ligaments that interconnect them] Chapter 28 On the Ossicles Which Resemble a Sesame Seed [Introduction] This chapter is illustrated in particular by the first figure at the beginning of chapter 25, showing the inner [palmar] surface of the hand together with the ossicles [ossa sesamoidea] to be described in this chapter, near the letters N, T, V, V, X, and Y, 1 of which N and T are also seen in the second figure of the chapter. Likewise, the second figure to be placed at the head of the thirty-third chapter serves the same purpose next to the letters m (which is also seen in the first figure), y, w, and *. Also, the figures illustrating the entire structure of bones shows these ossicles marked k. 2 The two ossicles located beneath the first internode in the big toe and marked w and y in the illustration just mentioned are drawn separately in this small diagram.

A here identifies the lower surface of the inner bone [y], the one that presses on the ground, B the upper surface of the same bone, which faces the head of the metatarsal bone supporting the toe, C the lower surface of the outer and lesser bone [w], D the upper. 3 Professors of anatomy have mentioned certain ossicles (these will be seen in the figures that I have included at the beginning of the chapter) which some say fill out the joints, tighten them, and strengthen them to make them less prone to dislocation. But I know no one to have written in which joints they are located or where they are found. Where the sesamoid ossicles are located Therefore I shall not be amiss if I add at this point in what places I have found ossicles of this kind, at the same time suggesting that each person also look for them in more joints than the ones I am about to explain. For I have observed them little by little over the passage of time in more joints than at first glance page 126 I noticed them. In the Hand First, two ossicles (T in figs 1 and 2, ch.

25) 4 are located in the inner surface of the second joint of the thumb, where its first bone is articulated to the second; they are quite round and solid, not differing much in their shape from a grain of rice: they are a little shorter than an actual grain. But as a grain of rice appears depressed on one side, so also is a part of these ossicles depressed, slightly hollowed and coated with cartilage on that part where they are both attached to the first bone of the thumb. They lie on the inside of the head of the first bone [caput ossis metacarpalis I] near the root of the head where it first begins to be covered and smoothed with cartilage [cartilago articularis]; one ossicle occupies the outer side of the inner surface of the head, and the other the inner side of the same surface. Both allow the tendon [m. flexor pollicis longus, tendo] (h and then q in the 6th table of muscles) that flexes the third bone of the thumb to be borne through the interval by which they are separated from each other.

Since these ossicles are strongly attached to that bone of the thumb, they are convex on the outside and resemble the part of a bone which puts forth ligaments and receives the insertion of tendons. In just this way two ossicles (V, V in fig. 1, ch. 25) are also found in the first internodes of the other fingers, 5 positioned in the same spot and smaller than the ossicles of the thumb the nearer you approach the little finger. The smallest and more or less cartilaginous ossicles are attached to the first joint of that finger [art. metacarpophalangealis V], or rather to the head of the metacarpal bone that supports the little finger. The remaining fingers are in an intermediate state. In old and (so to speak) bony people I have sometimes seen a single ossicle (corresponding to the one marked * in fig. 2, ch. 33) 6 located on the inner surface of the third joint of the thumb [art. interphalangealis pollicis], placed before the depression (L in fig 2, ch.

27) separating the heads of the second bone [phalanx proximalis] on its inner surface. Such an ossicle (X, X in fig. 1 ch. 25) has sometimes come to my attention in individual second and third finger joints, but so small as scarcely to equal the size of a millet seed. Unless you take the greatest care in cleaning bones, it may be discarded 7 (even as the ones in the first joints) along with the ligaments and never offer itself to view. An ossicle of noteworthy magnitude (N in figs. 1, 2, ch. 25) belonging to this type is generally observed where the metacarpal bone that supports the little finger is articulated to the eighth carpal bone [os hamatum]. This is how it is with the ossicles of the hand. The ossicles in the foot Similarly, in the foot we find one ossicle [os sesamoideum] (m in figs.

1, 2, ch 33) where the metatarsal bone 8 supporting the little toe [os digitorum V] is articulated with the bone that imitates a cube [os cuboideum], exactly corresponding to the last one I mentioned in the hand. In the first joints of the toes such ossicles (y, w in fig. 2, ch. 33) are hard to see, except in the toe; in the old, however, because they are rather large, they present themselves more readily. I have never found them in the second and third joints except in the second internode [art. interphalangealis hallucis] of the big toe, beneath which quite a large ossicle (* in the same figure) is attached. The ossicles which are placed under the first internode of the big toe are much more conspicuous, and the inner of these [y] is again far larger than the outer [w].

At the point where these are attached to the head of the metatarsal bone (which we shall explain enters the depression [facies articularis phalangis proximalis hallucis] of the first bone of the toe) they are slightly depressed, and being coated with cartilage they fit the convexity of that head handsomely. But on their lower surface [planta pedis] where they face the ground they are rounded, not unlike half of a hulled pea. 9 These are by far the most solid, and besides the fact that they are responsible for the first joint of the toe [art. metatarsophalangealis hallucis], they protect the tendon [m. flexor hallucis longus, tendo] (the ossicles will be seen below M in the 15th table of muscles; the tendon is d in the 14th table of muscles) by which the second bone of the big toe is flexed. They protrude on each side next to the tendon and elegantly prevent the tendon from being compressed by the pressure of the foot on the ground.

10 An ossicle more familiar to magicians and followers of occult philosophy The second of these ossicles is the one mentioned so often by magicians and followers of occult philosophy when they say there is a certain bone in man resembling a chickpea, immune to all corruption, which they aver will lie hidden in the earth after death like a seed and will bring a person forth on the final day of judgement. 11 It is surely one of these bones, most likely the outer one [w], quite like a hulled chickpea if you compare it to half of the chickpea. Or, if you join both bones, you will have made a whole chickpea, so far as the appearance is concerned. In larger men the inner bone [y] is so large that a die could easily be made from it. But these bones differ from the fictions of the Arabs in that they can be broken and burned like the other bones. Yet they are certainly somewhat resistant to decay, and, as has been said before, solid.

But debate over the doctrine by which they contend that a human being, whose infinite structure we are describing, is destined to be propagated out of such an ossicle we leave to theologians, who claim for themselves alone the free disputation and pronouncement about resurrection and the immortality of souls. Because of them, we shall offer no opinion about the marvelous and occult powers of the inner ossicle of the right big toe, no matter how much better the supply available to us of this bone from a hung thief or from time to time a lover, or from public dissections, than was available to those three ferocious harlots at Venice 12 who recently butchered an infant for the purpose of comparing this ossicle to the heart of a virgin boy and removed his living heart, and (as they richly deserved) paid the severest penalty for their crime. Albadaran That this ossicle was called Albadaran by the Arabs and by the truly occult and shadowy philosophers is better known by superstitious men than by students of anatomy, who may also be able to compare the fourth bone of the carpus [os pisiforme] to a chickpea.

13 Appendix The 1555 version of Chapter XXVIII In addition to the bones explained in the three preceding chapters, certain other small bones [ossa sesamoidea] (T, V, X, X in fig. 1, ch. 25) occur in the hand, compared by anatomists to sesame seeds. Of what sort they are, where they are situated, and what their number is in man or even in monkey, no one I know has either observed or described, and still less has the use of those bones been systematically set forth precisely and truly. It is therefore timely for me here to describe how many ossicles of this sort I have so far discovered in the careful examination of muscles and tendons. In the inspection of muscles rather than bones, I have found no unsatisfying number of these ossicles, as much in the foot as in the hand, since most and in fact nearly all are attached to tendons. Coated on only one surface with smooth, slippery cartilage, 14 they come into contact with the smooth, slippery surface of a bone. They are never attached to the bone by special ligaments.

The construction of the patella demonstrates the nature of sesamoids In just this way we see the bone (fig. for ch 32; see also * in the 6th table of muscles and k in the 8th) in front of the knee joint, which we call the patella, attached to tendons 15 which extend the tibia. Indeed, in no other way will you more readily discover the makeup of the sesamoid bones than from the structure of the patella; for these ossicles are seen immersed in tendons and attached to them so that with their hardness they may sustain and absorb the impact in certain motions of the bone on which the tendon so augmented and protected is stretched. And while they check the impact of the bone, one would justifiably think that they also prevent the bone against which they are placed from becoming easily dislocated from its joint. The patella, as by far the largest sesamoid, nicely demonstrates their nature. They are larger and, in a manner of speaking, more numerous the older the person and the more you dissect the human body to study the bones. In children they are still cartilaginous and not very conspicuous in the // p.

153 // tendons where they are contained. They also present themselves in dogs and monkeys, and generally in other quadrupeds more than in man, a moister 16 animal and one possessed of less hard bones. How many sesamoids occur in the hand A man who has achieved his full growth has two ossicles [ossa sesamoidea] (T in fig. 1, ch. 25 and T in fig. 2, ch. 25) in the anterior side of the second joint of the thumb, placed in front of the head of the first bone [caput ossis metacarpalis I] of the thumb which enters the depression of the second bone [phalanx proximalis], attached to tendons of the muscles (1, 2, 3 in the 7th table of muscles) [m. adductor pollicis] that originate from the palm and flex the second joint of the thumb. These ossicles, scarcely larger than a fenugreek seed, are situated at the sides of the anterior part of the joint and permit the tendon [m.

flexor pollicis longus, tendo] (q of muscle h in the 6th table of muscles) to ascend between them which will be thought to cause flexion of the thumb’s third joint. Just as these ossicles are seen at the second joint of the thumb, two others (V, V in fig.1, ch. 25) are seen at the first joints of the four fingers, smaller than the ones just mentioned, but like them contained in the short tendons of muscles [mm. interossei] that originate from the metacarpals and flex the first joints of the four fingers. On the anterior surface of the third joint of the thumb a single ossicle is discovered situated in front of the middle of the joint, its smooth surface matching the depression that is seen between the two capitula of the second bone of the thumb which go up into the depressions of the third bone for articulation. This ossicle is attached to the tendon [m. flexor pollicis longus, tendo] that flexes the third bone of the thumb and widens here for the joint. Another (X, X in fig. 1, ch.

25), much smaller than this and almost wholly cartilaginous, occurs in the second and third joint of the four fingers, matching the ossicle in the thumb joint in location and embedded in the tendon from which the joint to which the ossicle belongs obtains its flexion. How many sesamoids are observed in the foot All the sesamoids in the foot are identical with those of the hand, except that in the four toes they are much smaller and less easily seen to the degree that the fingers are larger than the toes. But as the big toe is formed of larger bones than the thumb, it has much larger ossicles [ossa sesamoidea] than the thumb. Two quite large sesamoids (y, w in fig. 2, ch. 33 and in the figure at the head of the present chapter) are placed beneath the first joint of the big toe next to the head of the metatarsal which is articulated to it. The inner [medial] of these is nearly half again as large as the outer nearer the second toe, more or less equal in size to half of a rather large pea cleaned of its skin, and even in its form it is not very unlike it.

These two ossicles of the toe are attached to the sinewy part of the muscles [m. flexor hallucis brevis] (b in the 14th table of muscles) that flex the first bone of the toe, near their insertion. The ossicle (* in fig. 2, ch. 33) beneath the second joint of the toe is embedded in the tendon [m. flexor hallucis longus, tendo] (d, d of muscle L in the 14th table of muscles) that flexes the second bone of the toe, and is much smaller still than the outer of those that belong to the first joint of the toe. Additional sesamoid ossicles To the class of ossicles that we are treating in this chapter, someone will perhaps add the ossicle (N in figs. 1 and 2, ch. 25) that we see occasionally in the hand next to the connection of the metacarpal bone supporting the little finger at the eighth carpal bone [os hamatum], which nearly faces the tendon [m.

extensor carpi ulnaris, tendo?] (d of muscle L in the 9th table of muscles) inserted here in the metacarpal, causing extension of the wrist. He will count two ossicles occurring in the back of the knee which are embedded in the heads (p, r, p, r, of muscles F, Y in the 12th table of muscles) of the first two muscles [m. gastrocnemius: caput mediale, caput laterale] that move the foot, early in their beginning from the femur. On their smooth and slippery surface where they project beyond the tissue of the muscles, these ossicles face the higher surface of the posterior region of the lower heads [condylus medialis, c. lateralis] (E, F in fig. 1, ch. 30) of the femur, whose movement they facilitate and support. Their special feature is that they are embedded at the beginning of muscles rather than in tendons, as are nearly all the other sesamoid ossicles.

To these will perhaps be added the bony part occurring in the tendon of old people which by a unique stratagem of Nature bends back to the bone resembling a cube (X of muscle V in the 15th table of muscles) and belongs to the seventh of the muscles [m. fibularis longus, tendo] that move the foot. To these belongs the ossicle (near to k 17 in fig. 2, ch. 33) found more than once at the outer side of the articulation of the metatarsal bone supporting the little toe and the tarsus, at the insertion // p. 154 // of the tendon (b of muscle a in the 15th table of muscles) of the eighth of the muscles [m. fibularis brevis] moving the foot. But of all these, none is as large and hard as the inner of the two ossicles which are seen on the first joint of the toe.

I therefore suspect that the magi and devotees of occult philosophy are thinking of this bone when they say there is a certain hard ossicle in man, subject to no corruption and resembling a chickpea; they aver that it lies in the earth after death like a seed, destined to bring a man forth on the final day of judgement. For this bone is situated in the lowest part of man and is especially hard. But even teeth lose their hardness, and this ossicle is no less subject to corruption than the teeth themselves. Moreover, the eighth carpal bone [os hamatum] (N in figs. 1, and 2, ch. 25) bears a better resemblance to a chickpea than this ossicle of the foot. The Albadaran ossicle 18 But whether the Arabs and the truly occult and shadowy philosophers believe rightly that man will be made again from this ossicle that they call the Albdaran, I leave theologians to dispute who claim free disputation and opinion about resurrection and the immortality and destiny of the soul. Book One -- The things that sustain and support the entire body, and what braces and attaches them all.

[the bones and the ligaments that interconnect them] Skeletal System – Labeled Diagrams of the Human Skeleton Pectoral (shoulder) girdle Skull The skull is composed of 22 bones that are fused together except for the mandible. These 21 fused bones are separate in children to allow the skull and brain to grow, but fuse to give added strength and protection as an adult. The mandible remains as a movable jaw bone and forms the only movable joint in the skull with the temporal bone . The bones of the superior portion of the skull are known as the cranium and protect the brain from damage. The bones of the inferior and anterior portion of the skull are known as facial bones and support the eyes, nose, and mouth. Hyoid and Auditory Ossicles The hyoid is a small, U-shaped bone found just inferior to the mandible. The hyoid is the only bone in the body that does not form a joint with any other bone—it is a floating bone. The hyoid’s function is to help hold the trachea open and to form a bony connection for the tongue muscles .

The malleus, incus, and stapes—known collectively as the auditory ossicles —are the smallest bones in the body. Found in a small cavity inside of the temporal bone, they serve to transmit and amplify sound from the eardrum to the inner ear. Vertebrae Twenty-six vertebrae form the vertebral column of the human body. They are named by region: Cervical (neck) - 7 vertebrae Sacrum - 1 vertebra Coccyx (tailbone) - 1 vertebra With the exception of the singular sacrum and coccyx, each vertebra is named for the first letter of its region and its position along the superior-inferior axis. For example, the most superior thoracic vertebra is called T1 and the most inferior is called T12. Ribs and Sternum The sternum, or breastbone, is a thin, knife-shaped bone located along the midline of the anterior side of the thoracic region of the skeleton . The sternum connects to the ribs by thin bands of cartilage called the costal cartilage. There are 12 pairs of ribs that together with the sternum form the ribcage of the thoracic region.

The first seven ribs are known as “true ribs” because they connect the thoracic vertebrae directly to the sternum through their own band of costal cartilage. Ribs 8, 9, and 10 all connect to the sternum through cartilage that is connected to the cartilage of the seventh rib, so we consider these to be “false ribs.” Ribs 11 and 12 are also false ribs, but are also considered to be “floating ribs” because they do not have any cartilage attachment to the sternum at all. Pectoral Girdle and Upper Limb The pectoral girdle connects the upper limb (arm) bones to the axial skeleton and consists of the left and right clavicles and left and right scapulae. The humerus is the bone of the upper arm. It forms the ball and socket joint of the shoulder with the scapula and forms the elbow joint with the lower arm bones. The radius and ulna are the two bones of the forearm. The ulna is on the medial side of the forearm and forms a hinge joint with the humerus at the elbow. The radius allows the forearm and hand to turn over at the wrist joint.

The lower arm bones form the wrist joint with the carpals, a group of eight small bones that give added flexibility to the wrist. The carpals are connected to the five metacarpals that form the bones of the hand and connect to each of the fingers. Each finger has three bones known as phalanges, except for the thumb, which only has two phalanges. Pelvic Girdle and Lower Limb Formed by the left and right hip bones, the pelvic girdle connects the lower limb (leg) bones to the axial skeleton. The femur is the largest bone in the body and the only bone of the thigh (femoral) region. The femur forms the ball and socket hip joint with the hip bone and forms the knee joint with the tibia and patella. Commonly called the kneecap, the patella is special because it is one of the few bones that are not present at birth. The patella forms in early childhood to support the knee for walking and crawling. The tibia and fibula are the bones of the lower leg. The tibia is much larger than the fibula and bears almost all of the body’s weight.

The fibula is mainly a muscle attachment point and is used to help maintain balance. The tibia and fibula form the ankle joint with the talus, one of the seven tarsal bones in the foot . The tarsals are a group of seven small bones that form the posterior end of the foot and heel. The tarsals form joints with the five long metatarsals of the foot. Then each of the metatarsals forms a joint with one of the set of phalanges in the toes. Each toe has three phalanges, except for the big toe, which only has two phalanges. Microscopic Structure of Bones The skeleton makes up about 30-40% of an adult’s body mass. The skeleton’s mass is made up of nonliving bone matrix and many tiny bone cells. Roughly half of the bone matrix’s mass is water , while the other half is collagen protein and solid crystals of calcium carbonate and calcium phosphate. Living bone cells are found on the edges of bones and in small cavities inside of the bone matrix. Although these cells make up very little of the total bone mass, they have several very important roles in the functions of the skeletal system.

The bone cells allow bones to: Grow and develop Be repaired following an injury or daily wear Be broken down to release their stored minerals Types of Bones All of the bones of the body can be broken down into five types: long, short, flat, irregular, and sesamoid. Long. Long bones are longer than they are wide and are the major bones of the limbs. Long bones grow more than the other classes of bone throughout childhood and so are responsible for the bulk of our height as adults. A hollow medullary cavity is found in the center of long bones and serves as a storage area for bone marrow. Examples of long bones include the femur, tibia, fibula, metatarsals, and phalanges. Short. Short bones are about as long as they are wide and are often cubed or round in shape. The carpal bones of the wrist and the tarsal bones of the foot are examples of short bones. Flat. Flat bones vary greatly in size and shape, but have the common feature of being very thin in one direction. Because they are thin, flat bones do not have a medullary cavity like the long bones.

The frontal, parietal, and occipital bones of the cranium—along with the ribs and hip bones—are all examples of flat bones. Irregular. Irregular bones have a shape that does not fit the pattern of the long, short, or flat bones. The vertebrae, sacrum, and coccyx of the spine—as well as the sphenoid, ethmoid, and zygomatic bones of the skull—are all irregular bones. Sesamoid. The sesamoid bones are formed after birth inside of tendons that run across joints. Sesamoid bones grow to protect the tendon from stresses and strains at the joint and can help to give a mechanical advantage to muscles pulling on the tendon. The patella and the pisiform bone of the carpals are the only sesamoid bones that are counted as part of the 206 bones of the body. Other sesamoid bones can form in the joints of the hands and feet, but are not present in all people. Parts of Bones The long bones of the body contain many distinct regions due to the way in which they develop. At birth, each long bone is made of three individual bones separated by hyaline cartilage.

Each end bone is called an epiphysis (epi = on; physis = to grow) while the middle bone is called a diaphysis (dia = passing through). The epiphyses and diaphysis grow towards one another and eventually fuse into one bone. The region of growth and eventual fusion in between the epiphysis and diaphysis is called the metaphysis (meta = after). Once the long bone parts have fused together, the only hyaline cartilage left in the bone is found as articular cartilage on the ends of the bone that form joints with other bones. The articular cartilage acts as a shock absorber and gliding surface between the bones to facilitate movement at the joint. Looking at a bone in cross section, there are several distinct layered regions that make up a bone. The outside of a bone is covered in a thin layer of dense irregular connective tissue called the periosteum. The periosteum contains many strong collagen fibers that are used to firmly anchor tendons and muscles to the bone for movement. Stem cells and osteoblast cells in the periosteum are involved in the growth and repair of the outside of the bone due to stress and injury.

Blood vessels present in the periosteum provide energy to the cells on the surface of the bone and penetrate into the bone itself to nourish the cells inside of the bone. The periosteum also contains nervous tissue and many nerve endings to give bone its sensitivity to pain when injured. Deep to the periosteum is the compact bone that makes up the hard, mineralized portion of the bone. Compact bone is made of a matrix of hard mineral salts reinforced with tough collagen fibers. Many tiny cells called osteocytes live in small spaces in the matrix and help to maintain the strength and integrity of the compact bone. Deep to the compact bone layer is a region of spongy bone where the bone tissue grows in thin columns called trabeculae with spaces for red bone marrow in between. The trabeculae grow in a specific pattern to resist outside stresses with the least amount of mass possible, keeping bones light but strong. Long bones have a spongy bone on their ends but have a hollow medullary cavity in the middle of the diaphysis. The medullary cavity contains red bone marrow during childhood, eventually turning into yellow bone marrow after puberty.

Articulations An articulation, or joint, is a point of contact between bones, between a bone and cartilage, or between a bone and a tooth. Synovial joints are the most common type of articulation and feature a small gap between the bones. This gap allows a free range of motion and space for synovial fluid to lubricate the joint. Fibrous joints exist where bones are very tightly joined and offer little to no movement between the bones. Fibrous joints also hold teeth in their bony sockets. Finally, cartilaginous joints are formed where bone meets cartilage or where there is a layer of cartilage between two bones. These joints provide a small amount of flexibility in the joint due to the gel-like consistency of cartilage. Skeletal System Physiology Support and Protection The skeletal system’s primary function is to form a solid framework that supports and protects the body's organs and anchors the skeletal muscles. The bones of the axial skeleton act as a hard shell to protect the internal organs—such as the brain and the heart —from damage caused by external forces. The bones of the appendicular skeleton provide support and flexibility at the joints and anchor the muscles that move the limbs.

Movement The bones of the skeletal system act as attachment points for the skeletal muscles of the body. Almost every skeletal muscle works by pulling two or more bones either closer together or further apart. Joints act as pivot points for the movement of the bones. The regions of each bone where muscles attach to the bone grow larger and stronger to support the additional force of the muscle. In addition, the overall mass and thickness of a bone increase when it is under a lot of stress from lifting weights or supporting body weight. Hematopoiesis Red bone marrow produces red and white blood cells in a process known as hematopoiesis. Red bone marrow is found in the hollow space inside of bones known as the medullary cavity . Children tend to have more red bone marrow compared to their body size than adults do, due to their body’s constant growth and development. The amount of red bone marrow drops off at the end of puberty, replaced by yellow bone marrow. Storage The skeletal system stores many different types of essential substances to facilitate growth and repair of the body. The skeletal system’s cell matrix acts as our calcium bank by storing and releasing calcium ions into the blood as needed.

Proper levels of calcium ions in the blood are essential to the proper function of the nervous and muscular systems. Bone cells also release osteocalcin, a hormone that helps regulate blood sugar and fat deposition. The yellow bone marrow inside of our hollow long bones is used to store energy in the form of lipids. Finally, red bone marrow stores some iron in the form of the molecule ferritin and uses this iron to form hemoglobin in red blood cells. Growth and Development The skeleton begins to form early in fetal development as a flexible skeleton made of hyaline cartilage and dense irregular fibrous connective tissue. These tissues act as a soft, growing framework and placeholder for the bony skeleton that will replace them. As development progresses, blood vessels begin to grow into the soft fetal skeleton, bringing stem cells and nutrients for bone growth. Osseous tissue slowly replaces the cartilage and fibrous tissue in a process called calcification. The calcified areas spread out from their blood vessels replacing the old tissues until they reach the border of another bony area.

At birth, the skeleton of a newborn has more than 300 bones; as a person ages, these bones grow together and fuse into larger bones, leaving adults with only 206 bones. Flat bones follow the process of intramembranous ossification where the young bones grow from a primary ossification center in fibrous membranes and leave a small region of fibrous tissue in between each other. In the skull these soft spots are known as fontanels, and give the skull flexibility and room for the bones to grow. Bone slowly replaces the fontanels until the individual bones of the skull fuse together to form a rigid adult skull. Long bones follow the process of endochondral ossification where the diaphysis grows inside of cartilage from a primary ossification center until it forms most of the bone. The epiphyses then grow from secondary ossification centers on the ends of the bone. A small band of hyaline cartilage remains in between the bones as a growth plate. As we grow through childhood, the growth plates grow under the influence of growth and sex hormones, slowly separating the bones. At the same time the bones grow larger by growing back into the growth plates.

This process continues until the end of puberty, when the growth plate stops growing and the bones fuse permanently into a single bone. The vast difference in height and limb length between birth and adulthood are mainly the result of endochondral ossification in the long bones. Prepared by Tim Taylor, Anatomy and Physiology Instructor Middle Ear Anatomy, Function & Diagram | Body Maps Your message has been sent. OK We're sorry, an error occurred. We are unable to collect your feedback at this time. However, your feedback is important to us. Please try again later. Close Middle ear Also known as the tympanic cavity, the middle ear is an air-filled, membrane-lined space located between the ear canal and the Eustachian tube, cochlea, and auditory nerve. The eardrum separates this space from the ear canal. The area is pressurized. The eardrum acts as a natural boundary between the middle ear and the ear canal. Pressure in the middle ear is maintained through the Eustachian tubes, which are closed when not in use. Each time a person swallows, the Eustachian tubes open and allow fresh air to enter into the tympanic cavity. This maintains a constant pressure gradient.

Sometimes, this pressure is not equalized with the environment outside the head, and this is often the reason why some people experience discomfort in airplanes and at higher elevations The cavity also plays a very important role in a person's ability to hear. Inside the middle ear, three small bones (ossicles) form a chain and conduct sound vibrations from the eardrum to the inner ear. Once in the fluid-filled inner ear, sounds are converted into nerve impulses and sent to the brain.

Question: In human anatomy, an ossicle is a very small what?
Answer: Bone